Novolak aralkyl resin, preparation process thereof and composition containing said resin

ABSTRACT

Preparation process for a novolak aralkyl resin having excellent heat resistance and curing property by reacting 0.4 to 0.8 mol of an aralkyl compound based on one mol of the low molecular weight novolak containing 90% by weight or more of bi-nuclear novolak in the presence of an acidic catalyst, the process comprising at first melting the low molecular weight novolak, heating it up to a reaction temperature, then adding 0.001 to 0.05% by weight of the acidic catalyst to the total amount of the low molecular weight novolak and the aralkyl compound, then continuously adding the aralkyl compound for reaction, neutralizing the residual acidic catalyst after the completion of the reaction, a novolak aralkyl resin obtained by the preparation process and a novolak aralkyl resin composition containing said resin.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a novolak aralkyl resin having bothstructural units of low molecular weight novolak units and aralkyl groupunits together and a preparation process thereof, and compositioncontaining the resin.

[0003] More in particular, it relates to a novolak aralkyl resin whichis heightened its molecular weight while increasing the repeatingstructural units of low molecular weight novolak units and aralkyl groupunits by suppressing decomposition of low molecular weight novolak,makes its curing reaction with hexamethylenetetramine or the likeprogress uniformly and rapidly, provides excellent heat resistance toits cured products and suitable to application uses such as frictionmaterials, sliding materials, molding materials and encapsulatingmaterials, a preparation process thereof, a novolak aralkyl resincomposition causing rapid curing reaction and providing excellent heatresistance to its cured products which is suitable to friction materialssuch as disk brake pads, brake linings and clutch facings for brakingautomobiles, railway vehicles and various industrial machines, tobinders for molding materials such as electric and electronic equipmentparts, communication equipment parts and mechanical parts and to slidingmaterials and so on.

[0004] In this invention, novolak means, resins having a repeatingstructure of phenol nuclear units and methylene group units obtained byreacting, for example, phenol and formaldehyde in the presence of anacidic catalyst. They are referred to bi-nuclear novolak, tri-nuclearnovolak and the like depending on the number of phenol nuclear units.Further, low molecular weight novolak is a collective term for novolaksup to about penta-nuclear novolak.

[0005] 2. Related Art Statement

[0006] A phenolic resin as a reaction product of a phenol compound andan aralkyl compound such as p-xylylene glycol dimethyl ether isgenerally referred to as a xylok resin which is a phenol aralkyl resinhaving a repeating structure of phenol nuclei and aralkyl group asdescribed, for example, in Japanese Patent Publication No. 15111/1972and Japanese Patent Publication No. 14280/1977. The phenol aralkyl resinhas excellent characteristics for heat resistance, soft and flexibilityand hygroscopic resistance compared with novolak type phenol resin andhas been generally used for applications such as friction materials,molding materials and encapsulating materials. However, in the fieldwhere it is used by being cured with hexamethylenetetramine or the like,since the ratio of the phenol nuclei is small in the resin, the curingreaction is slow for which improvement has been desired.

[0007] For compensating the drawback, Japanese Patent Laid-Open No.142324/1992 proposes a modified phenol aralkyl resin obtained byreacting phenols, an aralkyl compound and formaldehyde in the presenceof an acidic catalyst at 100 to 150° C. Further, Japanese PatentLaid-Open No. 173834/1992 discloses a phenolic resin of using phenol andnovolak resin together, which is reacted with p-xylylene glycol dimethylether. However, since phenol is used as the raw material in the bothresins described above, they contain a phenol aralkyl resin portioncausing slow curing reaction, their curing rate are insufficient. Inaddition, though a novolak resin portion is present during reaction inthe method described in both of the publications, when the novolak resinhas high molecular weight, it further is heightened molecular weightremarkably or gelled in the subsequent reaction, so that the amount ofthe aralkyl compound to be introduced can not be increased and, as aresult, the amount of unreacted novolak resin increases to bring about aproblem of lowering the heat resistance. Further, since the amount ofthe acidic catalyst used is large, it involves a problem that thecatalyst remaining in the resin causes decomposing reaction, failing toobtain a resin of stable property.

[0008] In addition, there can be mentioned a method of increasing thevelocity of curing reaction by mixing a novolak type phenol resin withthe phenol aralkyl resin, but since the novolak type phenol resin reactspreferentially to hexamine or the like, this results in a problem ofunevenness in the curing.

[0009] When novolak, particularly, a low molecular weight novolak and anacidic catalyst are brought into contact, it causes decomposition andre-bonding to form phenol and high molecular weight novolak.Accordingly, decomposition and re-bonding reaction are also caused in acase of reacting the low molecular weight novolak with the aralkylcompound in the presence of the acidic catalyst, so that it leads to aproblem that a stable reaction product containing many repeatingstructural units of low molecular weight novolak and aralkyl groups cannot be obtained.

DISCLOSURE OF THE INVENTION

[0010] This invention intends to provide a novolak aralkyl resin havingboth structures of bi-nuclear novolak units and aralkyl group unitstogether and being capable of conducting the curing reaction withhexamethylenetetramine or the like rapidly and uniformly whilemaintaining the excellent heat resistance inherent to the phenol aralkylresin, and a preparation process thereof, and a composition containingthe novolak aralkyl resin described above.

[0011] An aimed novolak aralkyl resin can be obtained by increasing therepeating structural units of bi-nuclear novolak units and aralkyl groupunits and by increasing the molecular weight of the resin. In this case,it is important to suppress the decomposing reaction of the lowmolecular weight novolak. Novolak causes decomposition and re-bonding bybeing heated in the presence of an acidic substance to form phenol andhigh molecular weight novolak. For example, when a bi-nuclear novolak asa typical example of the low molecular weight novolak is heated forabout one hour in the presence of the same acidic catalyst and at thesame temperature as upon reaction with the aralkyl compound, about 8 mol% phenol is formed, and twice molar amount of bi-nuclear novolak is lostand tri-or higher poly-nuclear novolak is formed. On the other hand,when the reaction velocity with the aralkyl compounds is comparedbetween the low molecular weight novolak and phenol, the reactionvelocity is higher for the low molecular weight novolak. For example,when the mixture of bi-nuclear novolak and phenol containing each at anequal molar amount is reacted with the aralkyl compound, it results inmore unreacted component for phenol.

[0012] Accordingly, even if the bi-nuclear novolak and the aralkylcompound are charged each by a predetermined amount for reaction intothe reaction system, when the decomposition of the bi-nuclear novolakproceeds, reaction is taken place for three ingredients of novolak,phenol and aralkyl compound and the properties of the resultant resin isdeviated from desired values depending on the extent of thedecomposition. Further, after the completion of the reaction, in a casewhere the decomposition proceeds while liberating a phenol, theresultant resin becomes instable because of bonding of disconnectedactive residues with other molecules of bi-nuclear novolak or the like.Consequently, the molecular weight of the resultant resin becomeshigher.

[0013] From the foregoings, as a means for obtaining a resin containingmany repeating structural units of low molecular weight novolak andaralkyl groups, it is important to suppress the decomposing reaction ofthe low molecular weight novolak and to avoid the formation of the freephenol as an index of the decomposition of raw materials such as lowmolecular weight novolak as less as possible.

[0014] The present inventors have made an earnest study on the basis ofthe knowledge as described above, as a result, have found that thedecomposition of the low molecular weight novolak during the reactioncan be suppressed to obtain an aimed resin upon reacting low molecularweight novolak containing a bi-nuclear novolak at a specified amount ormore and an aralkyl compound in the presence of an acidic catalyst bysuppressing contact of the acidic catalyst only with the low molecularweight novolak as the raw material, restricting the amount of thecatalyst to a required minimum level as less as possible and, further,neutralizing the acidic catalyst after the completion of the reaction,and have accomplished this invention.

[0015] That is, the first feature of this invention resides in apreparation process for a novolak aralkyl resin by reacting 0.4 to 0.8mol of an aralkyl compound based on one mol of a low molecular weightnovolak containing 90% by weight or more of a bi-nuclear novolak inpresence of an acidic catalyst, wherein comprising at first melting thelow molecular weight novolak and heating it up to a reactiontemperature, then adding 0.001 to 0.05% by weight of the acidic catalystbased on the total amount of the low molecular weight novolak and thearalkyl compound, then continuously adding the aralkyl compound forreaction, neutralizing the residual acidic catalyst after the completionof the reaction.

[0016] As a preferred embodiment for the preparation process for thenovolak aralkyl resin described above, there can be mentioned a methodof using p-xylylene glycol dimethyl ether as an aralkyl compound, amethod of practicing the reaction at a reaction temperature within arange of 130 to 160° C., a method of using hydroxides of calcium,barium, magnesium or a mixture of such metals as a neutralizing agent.

[0017] The second feature of this invention resides in a novolak aralkylresin obtained by the preparation process described above. The resin isa novolak aralkyl resin represented by the general formula (1):

[0018] wherein m is an integer of 1 to 4 and n is an integer of 1 to10,000, in which the ratio of the low molecular weight novolak unit withm being 1 based on low molecular weight novolak unit with m being 1 to 4in the general formula (1) described above is at least 80% by weight,the hydroxyl equivalent is 120 to 145 g/eq, and the content of the freephenol is 2% by weight or less.

[0019] The third feature of this invention resides in a novolak aralkylresin composition containing 80 to 95% by weight of the novolak aralkylresin described above and 5 to 20% by weight of thehexamethylenetetramine. The resin composition has such characteristicsthat the 90% curing time at 150° C. is 7 to 12 minutes and the weightretention ratio after storage at 300° C. for 240 hours is 70% or more.

[0020] A molding base material or a solvent may be added to the resincomposition depending on the application use. When the molding basematerial is added, 80 to 95% by weight of at least one molding basematerial selected from the group consisting of reinforcing fibers,lubricants and fillers is added based on 5 to 20% by weight of the resincomposition. Further, when the solvent is added, 30 to 70% by weight ofan organic solvent is added based on 30 to 70% by weight of the resincomposition. A preferred solvent can include methanol, ethanol, methylethyl ketone, butyl cellosolve, butyl carbitol or a mixture of them.

[0021] The fourth feature of this invention is a novolak aralkyl resincomposition containing 10 to 75% by weight of the novolak aralkyl resindescribed above, 25 to 90% by weight of an epoxy resin and 0.01 to 5% byweight of a curing catalyst based on the total amount of both of theresins.

[0022] In a case where the resin composition is used, for example, as aencapsulating material, 100 to 190 parts by weight of an organic filler,inorganic filler or a mixture thereof is added based on 100 parts byweight of the resin composition.

[0023] According to this invention, decomposition of the low molecularweight novolak can be suppressed in the entire preparation steps fromthe charging of the raw materials to the formation of a novolak aralkylresin, consequently, the novolak aralkyl resin with a high ratio of BPFunit based on the low molecular weight novolak unit with m being 1 to 4in the general formula (1) can be obtained. The novolak aralkyl resincontains many repeating structures of BPF units and aralkyl group units.Since the novolak aralkyl resin according to this invention has the sameheat resistance substantially as existent phenol aralkyl resins andconducts the curing reaction with hexamethylenetetramine or the likeuniformly and rapidly. Therefore, a resin composition containing thenovolak aralkyl resin according to this invention has both excellentheat resistance and moldability. Accordingly, the novolak aralkyl resinand the composition containing the resin of this invention can be usedsuitably as binders for molding materials such as friction materials fordisk brake pads, brake linings and clutch facings used for brakingautomobiles, railway vehicles and various industrial machine, electricand electronic equipment parts, communication equipment parts andmachine parts, sliding materials, semiconductor encapsulating materials,lamination materials, coatings and adhesives.

[0024] The ratio of the low molecular weight novolak unit with m being 1based on the low molecular weight novolak unit with m being 1 to 4 inthe general formula (1) described above in the novolak aralkyl resinaccording to this invention means a value determined by a method shownin the example to be described later. In this invention, the lowmolecular weight novolak unit with m being 1 in the general formula (1)means a bi-nuclear novolak unit.

PREFERRED EMBODIMENTS OF THE INVENTION

[0025] This invention is to be described in details. At first, apreparation process for a novolak aralkyl resin according to the firstfeature of this invention is to be described. The outline of thepreparation process for the novolak aralkyl resin according to thisinvention is as follows. The preparation process, which comprisesreacting a low molecular weight novolak containing a specified amount ormore of a bi-nuclear novolak (hereinafter simply referred to as BPF)with an aralkyl compound in the presence of a relatively small amount ofan acidic catalyst and neutralizing the residual catalyst after thecompletion of the reaction.

[0026] Usually, the low molecular weight novolak includes a novolakresin with 65% by weight or more of BPF content obtained by reactingabout 6 to 30 moles of phenol with 1 mole of formaldehyde in thepresence of an acidic catalyst and then removing unreacted phenol(hereinafter simply referred to as de-phenol product), and a novolakresin with 90% by weight or more of BPF obtained by distillation fromthe de-phenol product, and a novolak resin with non-distilledtri-nuclear novolak as the main ingredient. The amount of BPF in the lowmolecular weight novolak gives an effect on the heat resistance of theresultant resin. When the amount of BPF is smaller, the ratio of the BPFunit in the resultant novolak aralkyl resin is lowered and the repeatingstructure of the BPF units and the aralkyl units is decreased. That is,since the novolak resin portion is increased, the heat resistance of theresultant resin is lowered. Further, it is preferred to use the lowmolecular weight novolak having stable composition such as the BPFcontent as the raw material for producing a novolak aralkyl resin havingstable qualities. With a view point described above, it is preferred inthis invention to use a low molecular weight novolak with the BPFcontent of 90% by weight or more in the low molecular weight novolakdescribed above.

[0027] The aralkyl compound used in this invention, can include, forexample, α, α′-dichloro-p-xylene, α, α′-dichloro-o-xylene, α,α′-dichloro-m-xylene, p-xylylene glycol, p-xylylene glycol dimethylether (hereinafter simply referred to as PXDM), α,α′-dimethoxy-o-xylene, α, α′-dimethoxy-m-xylene, and α,α′-dimethoxy-p-xylene. A preferred aralkyl compound is PXDM.

[0028] As PXDM, a high purity product of 98% by weight or more ispreferred. A PXDM obtained industrially usually contains impurities suchas α-methoxy-p-xylene, α, α-dimethoxy-p-xylene, α, α,α′-trimethoxy-p-xylene, p-xylylene glycol and p-xylylene glycolmonomethyl ether. However, there is no problem when the amount of theimpurities is less than 2% by weight.

[0029] The amount of the low molecular weight novolak and the aralkylcompound used gives an effect on the curing reaction withhexamethylenetetramine (hereinafter simply referred to as hexamine) orthe like and the heat resistance of the resultant resin. For obtaining aresin having excellent heat resistance and curing reactivity, it ispreferred to use 0.4 to 0.8 mole of the aralkyl compound based on onemole of the low molecular weight novolak. A further preferred amount ofthe aralkyl compound is 0.5 to 0.75 mole. When the amount of the aralkylcompound used exceeds 0.8 mole, high molecular weight novolak alalkylresin increases remarkably or gelation of the resin occurs.Consequently, the aimed resin can not be obtained. On the contrary, whenit is less than 0.4 mole, since unreacted low molecular weight novolakincreases, the molecular weight of the resin is not increased and theheat resistance of the resin is lowered.

[0030] The low molecular weight novolak and the aralkyl compound arereacted in the presence of an acidic catalyst. As Preferable acidiccatalyst, for example, zinc chloride, stannic chloride, sodium hydrogensulfate, sulfuric acid, hydrochloric acid, oxalic acid, monoethylsulfuric acid, diethyl sulfate, phenol sulfonic acid and p-toluenesulfonic acid are illustrated. Diethyl sulfate is more Preferable. Forsuppressing the decomposition reaction of the low molecular weightnovolak and completing the condensation reaction rapidly, the amount ofthe acidic catalyst used is preferable within a range from 0.001 to0.05% by weight based on the total amount of the low molecular weightnovolak and the aralkyl compound as using the raw materials. A furtherpreferred range is from 0.005 to 0.02% by weight. When the amountexceeds 0.05% by weight, decomposition of the low molecular weightnovolak increases. On the contrary, when the amount is less than 0.001%by weight, the reaction velocity is lowered.

[0031] In the presence of the acidic catalyst, change of the propertiesoccurs in the resultant resin even after the aralkyl compound has beenconsumed thoroughly to complete the reaction. Specifically, unreactedlow molecular weight novolak and the novolak resin portion of theresultant resin are decomposed while liberating phenol and re-bondedwith them to become high molecular weight resin. Accordingly, forstabilizing the properties of the resin, it is important to conductneutralization of the residual acidic catalyst after the completion ofthe reaction.

[0032] There is no particular restriction on the neutralizing agent solong as it is basic, hydroxides of alkali metals such as lithium, sodiumand potassium or alkaline earth metals such as magnesium, calcium orbarium are preferred. Hydroxide of magnesium, calcium or barium isfurther preferred. Barium hydroxide which gives less effect on theproperties of the resin and which neutralization salt to be formed isused as a filler for friction materials is further preferred.

[0033] The amount of the neutralizing agent used is preferably from 0.8to 1.1 equivalent based on the acidic catalyst while depending on theamount of the acidic catalyst used. 1.0 equivalent is most preferred.When it is less than 0.8 equivalent, non-neutralizing acidic catalystundesirably causes change of the properties of the resin. On the otherhand, when it exceeds 1.1 equivalent, the resin is undesirably tintedyellow.

[0034] When PXDM is used as the aralkyl compound, it is also useful touse a small amount of methanol upon practicing this process. Though thereaction of the low molecular weight novolak with PXDM by-producesmethanol, elevation of the reaction temperature at the initial stage ofthe reaction can be prevented by previously adding the small amount ofmethanol prior to the start of the reaction. That is, though heat isgenerated upon starting of the reaction and the internal temperaturerises till the by-produced methanol is saturated in the reaction system,the internal temperature elevation can be prevented by previously addingthe saturation amount of methanol, which leads to the effect ofpreventing decomposition of the low molecular weight novolak. The amountof methanol to be added is preferably 2 to 4% by weight based on the lowmolecular weight novolak, for example, in a case where the reactiontemperature is 130 to 160° C.

[0035] In addition to the ingredients described above, addition ofcommercial defoamer silicone is also useful. Particularly, in a case ofproducing a high molecular weight resin, it can provide an effect ofeasily withdrawing by-produced methanol from the reaction system toprevent rise of the liquid surface of the reaction product and furthershorten the time of operation such as removal of methanol conductedunder a reduced pressure. A preferred addition amount of the silicone is10 to 20 ppm based on the resin formed.

[0036] A preferred embodiment of the preparation process according tothis invention is as described below. After charging a low molecularweight novolak and a small amount of methanol into a reactor andelevating the temperature up to reaction temperature, an acidic catalystis added. Then, continuous charging of PXDM is initiated. Charging ofPXDM is continued while distilling off the by-produced methanol and,when charging of a predetermined amount of the PXDM is completed, agingreaction is conducted to complete the reaction. Then, the catalyst isneutralized and a trace amount of methanol and water dissolved thereinare removed under a reduced pressure.

[0037] The reaction temperature is preferable within a range from 120 to200° C. A more preferred range is from 130 to 160° C. When it is lowerthan 120° C., the reaction velocity is extremely slow. On the otherhand, when it exceeds 200° C., decomposition of the low molecular weightnovolak used as raw materials and the reaction product increases.Further, in a case of using PXDM as the aralkyl compound, a portion ofPXDM is extracted together with by-produced methanol out of the reactionsystem.

[0038] Even though the low molecular weight novolak with a high BPFcontent is used as raw material, when the decomposition of the lowmolecular weight novolak during reaction increases, the ratio of the BPFunit in the resultant novolak aralkyl resin is lowered, and it resultsin decreasing of the repeating structure of the BPF units and thearalkyl units. That is, since the novolak resin portion increases, theheat resistance of the resultant novolak aralkyl resin is lowered.Accordingly, it is necessary to react by a method of suppressing thedecomposition of the low molecular weight novolak.

[0039] The decomposition of the low molecular weight novolak takes placemost remarkably in the step from the instance the catalyst is added tothe start of the charging of the aralkyl compound. Therefore, it leadsto the prevention of decomposition to shorten the time of contact onlybetween the low molecular weight novolak and the catalyst. Accordingly,it is preferred to start the charging of the aralkyl compoundimmediately after addition of the catalyst. Further, for obtaining aresin having stable characteristics, it is preferred to shorten the timeof contact only between the low molecular weight novolak and thecatalyst as less as possible. The shorter contact time is more preferredfor reducing the deviation in the characteristics of the resin, it ispreferably less than 30 minutes, particular preferably, less than 15minutes. If necessary, a portion of the aralkyl compound to be chargedmay be present in the reaction system before addition of the catalyst.

[0040] The method of suppressing the decomposition of the low molecularweight novolak can include a method of charging the whole raw materialsat the same time and a method of adding the catalyst continuously.Specifically, the former is a method of charging the low molecularweight novolak, the aralkyl compound and the catalyst at the same time,then initiating the reaction, while the latter is a method of chargingthe low molecular weight novolak and the aralkyl compound at the sametime, then continuously adding the catalyst such as hydrochloric acid toconduct reaction. Each of the methods can suppress the decomposition ofthe low molecular weight novolak and suppress the formation of phenol.However, they involve such problems that the control for the reactionvelocity or the molecular weight is difficult, the reactor efficiency ispoor, high molecular weight compound insoluble to the solvent is formedon the reactor wall and a great amount of catalyst is required.

[0041] As a result of considering them, the present inventors havereached a preparation process of this invention of at first charging thelow molecular weight novolak, elevating the temperature up to thereaction temperature, adding the acidic catalyst and then instantlystarting the continuous charging of the aralkyl compound.

[0042] The continuous charging time of the aralkyl compound depends onthe molar ratio of the raw materials, the reaction temperature and thescale of the reaction. It is usually from 30 minutes to 10 hours at thepreferred reaction temperature described above. It is preferably, 1 to 6hours. When it is less than 30 minutes, unreacted aralkyl compoundincreases to require a long time for the aging reaction substantially.On the contrary, if it exceeds 10 hours, decomposition of the lowmolecular weight novolak increases and the productivity is lowered.

[0043] The aging reaction is conducted till the completion of thereaction. Completion of the reaction means that the unreacted aralkylcompound is no more present in the reaction system. Though the agingtime required differs depending on the amount of the catalyst, thereaction temperature and the charging time of the aralkyl compound, itis about 30 minutes to 5 hours. For example, it requires about threehours in a case where PXDM is used for the aralkyl compound, thecatalyst is used by 0.01% by weight based on the total amount of the lowmolecular weight novolak and the PXDM, the reaction temperature is setat 145° C. and PXDM is charged for three hours for reaction.

[0044] Since decomposition proceeds also even after the completion ofthe reaction by the contact of the reaction product and the unreactedlow molecular weight novolak with the acidic catalyst, to give an effecton the properties of the resultant resin, it is important to instantlyneutralize the residual catalyst after the completion of the agingreaction. Particularly, since the pressure reduction step and thedischarging operation are conducted at a high temperature for a longtime, neutralization of the residual catalyst gives a significant effectfor the stabilization of the properties of the resin. The neutralizingagent may be added either in the form a solid as it is or in the form ofa solution. Since the amount of it to be used is small amount, it iseffective to conduct neutralization in the form of an aqueous solutionfor rapid neutralization. Since the reaction liquid after theneutralization contains a small amount of methanol and water containingneutralization agent dissolved therein, they are distilled off under areduced pressure.

[0045] In the preparation process according to this invention, since amethod of charging the low molecular weight novolak, elevating thetemperature up to the reaction temperature, adding a specified amount ofthe acidic catalyst and then continuously charging the aralkyl compoundis adopted, therefore, the decomposition reaction of the low molecularweight novolak and the reaction product that occurs from the charging ofthe raw material to the completion of the condensation reaction can besuppressed. Accordingly, the novolak aralkyl resin obtained by thepreparation process according to this invention contains 2% by weight orless of free phenol formed mainly by the decomposition of the lowmolecular weight novolak. The free phenol optionally can be reducedfurther by being removed strictly under a reduced pressure. The contentof the free phenol is most preferably 0% by weight. The content of thefree phenol of 2% by weight or less formed by the decomposition of thelow molecular weight novolak means that the decomposition amount of thelow molecular weight novolak is 5 mol % or less. When the decompositionis kept at such an extent or less, a resin having desired properties canbe obtained by using the low molecular weight novolak and the aralkylcompound at a predetermined ratio.

[0046] In the preparation process for the novolak aralkyl resinaccording to this invention, since the low molecular weight novolak asthe raw material is used in excess relative to the aralkyl compound andsince the reaction is conducted while suppressing the decomposition ofthe low molecular weight novolak till the aralkyl compound is no morepresent in the reaction system, the resultant resin contains 8 to 20% byweight of BPF. Accordingly, the resin with the BPF content of less than8% by weight with no particular operation for removing BPF shows thatthis is a resin suffering from remarkable decomposition of the lowmolecular weight novolak.

[0047] The unreacted BPF can also be decreased optionally, for example,by a method of distillation, hot water extraction or steam strippingunder the conditions at a temperature of 200 to 250° C. and at apressure of 0.1 to 6.7 kPa. The resin removed with the unreacted BPF hasa feature of having only the repeating structure of the low molecularweight novolak units and the aralkyl group units. Further, unreacted BPFcan be decomposed and reduced also by continuing heating withoutneutralization even after the completion of the condensation reaction,but the properties of the resultant resin are remarkably changedundesirably.

[0048] The second feature of this invention resides in the novolakaralkyl resin obtained by the preparation process described previously.According to the preparation process for the resin, the decompositionreaction of the low molecular weight novolak and the reaction productthat occurs during reaction of the low molecular weight novolak with thearalkyl compound is suppressed. Accordingly, in the novolak aralkylresin according to the second feature of this invention, the ratio ofthe low molecular weight novolak with m being 1 based on a low molecularweight novolak unit with m being 1 to 4 in the general formula (1)described above is at least 80% by weight. The novolak aralkyl resinhaving such a structure is excellent in the heat resistance and has highcuring reaction velocity.

[0049] The novolak aralkyl resin according to the second feature of thisinvention produced as described above has a hydroxyl equivalent of 120to 145 g/eq. It is preferably from 130 to 140 g/eq. When it is less than120 g/eq, the resin is of low molecular weight with less aralkyl groupratio and many unreacted low molecular weight novolak is contained andheat resistance is low. When it exceeds 145 g/eq, the resin has anextremely high molecular weight and the molding becomes difficult.

[0050] The hydroxyl equivalent can be forecast approximately based onthe ratio of the low molecular weight novolak and the aralkyl compoundused. Even though the decomposition occurs remarkably and much phenol isformed, it is possible to obtain a resin of the preferred rangedescribed above unless the phenol is removed out of the reaction system.Further, the resin having similar hydroxyl group equivalent can beobtained also by a method of mixing the phenol aralkyl resin and thenovolak resin, a method of using phenol and novolak together to reactthem with PXDM as described in Japanese Published Unexamined PatentLaid-open No. 173834/1992. However, even though the hydroxyl equivalentis adjusted within the range as specified in this invention by thesemethods described above, the resin represented by the general formula(1) according to this invention can not be obtained and the curingreaction with hexamine or the like proceeds not uniformly.

[0051] According to the preparation process of this invention,decomposition of the low molecular weight novolak during thecondensation reaction is suppressed. Accordingly, it is possible toobtain a novolak aralkyl resin having less content of the free phenol asthe index of the decomposition, having a high ratio of the BPF unitbased on the low molecular weight novolak units with m being 1 to 4 inthe general formula (1) described above and containing many repeatingstructures of the BPF units and the aralkyl group units. Since thenovolak aralkyl resin according to this invention conducts curingreaction with hexamine or the like uniformly and rapidly, it is possibleto obtain a resin composition suitable to friction materials by mixingwith hexamine and molding materials such as reinforcing fiber, lubricantor filler. Further, since the acidic catalyst has been neutralized, astable modified resin is obtained also in a case of modifying with asilicone rubber. Further, when it is used as a curing agent of an epoxyresin, since the hydroxyl equivalent is small, it provides a meritcapable of decreasing the amount to be used.

[0052] Then, description is to be made to a novolak aralkyl resincomposition according to the third feature of this invention. Thenovolak aralkyl resin composition according to this invention isproduced by adding and mixing a specified amount of hexamine to thenovolak aralkyl resin described above. There is no particularrestriction on the mixing method and it can include, for example, amethod of pulverizing and finely powderizing while mixing by using apulverizer or the like. The mixing temperature is preferably near theroom temperature.

[0053] The blending ratio of the hexamine with the novolak aralkyl resingives an effect, for example, on the curing velocity, curing degree,heat resistance of curing product and the operation circumstance. Whenthe addition amount of the hexamine is insufficient, the curing velocityof the resin is slow, no sufficient curing degree is obtained and it isdifficult to obtain a cured product having excellent heat resistance. Onthe contrary, if the addition amount is excessive, excess hexamine isdecomposed to evolve a great amount of ammonia, which is not preferredin view of the operation circumstance. Considering them, it is preferredto mix 80 to 95% by weight of the novolak aralkyl resin and 5 to 20% byweight of hexamine. Further preferably, it is within a range from 87 to93% by weight of the novolak aralkyl resin and from 7 to 13% by weightof hexamine.

[0054] The novolak aralkyl resin composition according to the thirdfeature of this invention requires a short time to reach 90% curingratio of 7 to 12 minutes when cured at 150° C. and the curing velocityis extremely high compared with existent phenol aralkyl resins. Further,the molding product obtained by curing the resin composition at 150° C.has a weight retention ratio of 70% or more after storage at 300° C. for240 hours and shows excellent heat resistance much more than the novolakresin and shows the same heat resistance as the phenol aralkyl resin.Accordingly, the novolak aralkyl resin composition according to thisinvention is a novel resin composition having the excellent heatresistance and high speed molding property together.

[0055] When the resin composition according to the third feature of thisinvention is used, for example, to a friction material, it is preferredto add molding base materials such as reinforcing fibers, lubricants andfillers to the resin composition containing the novolak aralkyl resinand the hexamine as described above. In this case, they are mixed withina range of 5 to 20% by weight of the resin composition containing thenovolak aralkyl resin and the hexamine and 80 to 95% by weight of atleast one molding base material selected from the group consisting ofreinforcing fibers, lubricants and fillers.

[0056] The reinforcing fiber in this invention can include inorganic,organic and metal fibers such as glass fibers, carbon fibers, alamidefibers and steel fibers. The lubricant can include, graphite, antimonysulfide and molybdenum sulfide. Further, the filler can include, forexample, cashew dust, barium sulfate, calcium carbonate, magnesiumcarbonate, silica and metal powder. The molding base material may beused singly, or two or more of them may be used as a mixture.

[0057] When the resin composition according to this invention is used,for example, to wet friction materials, adhesives or sliding materials,it is preferred to add a solvent to the resin composition containing theresin and the hexamine. In this case, 30 to 70% by weight of the resincomposition containing the novolak aralkyl resin and hexamine and 30 to70% by weight of the solvent are mixed to dissolve the resincomposition. A preferred solvent can include at least one solventselected from the group consisting of methanol, ethanol, methyl ethylketone, butyl cellosolve and butyl carbitol.

[0058] Then, description is to be made to a novolak aralkyl resincomposition according to the fourth feature of this invention. Thenovolak aralkyl resin composition according to this invention is alsoprepared by mixing the novolak aralkyl resin described above, an epoxyresin and a curing catalyst. There is no particular restriction on themixing method and, for example, a method of dissolving each of them in asolvent or a pulverization mixing method. The mixing temperature ispreferably near the room temperature. A cured product is obtained byapplying a heat treatment to the novolak aralkyl resin compositionaccording to this invention within a temperature range usually from 100to 250° C.

[0059] The epoxy resin may be any epoxy resin so long as two or moreepoxy groups are contained in one molecule and it can include, forexample, bisphenol-A type epoxy resin, bisphenol-F type epoxy resin,phenol novolak type epoxy resin, cresol novolak type epoxy resin,glycidyl ether type epoxy resin such as tetramethyl biphenyl type epoxyresin, cycloaliphatic epoxy resin such as (3′, 4′-epoxy cyclohexylmethyl)-3-4-epoxy cyclohexane carboxylate. Two or more of the epoxyresins may be used together. Typical commercial products of the cresolnovolak type epoxy resin can include, for example, EOCN-102S; trade nameof product manufactured by Nippon Kayaku Co.

[0060] The blending ratio of the epoxy resin to the novolak aralkylresin gives an effect on the curing velocity, the curing degree, and theheat resistance and hygroscopic resistance of the curing product. Whenthe blending amount of the novolak aralkyl resin is insufficient, thecuring velocity of the resin composition is slow, no sufficient curingdegree is obtained and it is difficult to obtain a cured product havingexcellent heat resistance and hygroscopic resistance. Further, when theblending ratio is excessive, the performances described above can not beprovided at a good balance, which is also not preferred. In view of theabove, it is preferred to mix the novolak aralkyl resin from 10 to 75%by weight and the epoxy resin from 25 to 90% by weight being expressedby weight percentage. Further preferably, the novolak aralkyl resinranges from 15 to 70% by weight and the epoxy resin ranges from 30 to85% by weight. Further, the equivalent ratio of the hydroxyl groups inthe novolak aralkyl resin and the epoxy groups in the epoxy resin isfrom 0.5 to 1.5 molar equivalent amount and, preferably, from 0.7 to 1.3molar equivalent amount of the hydroxyl groups based on 1 molarequivalent amount of the epoxy group and it is preferred to adjust themolar ratio so as to obtain the optimal properties of the curingproduct.

[0061] The curing catalyst can include, for example, organic phosphinecompounds such as triphenyl phosphine, imidazole compounds such as2-ethyl-4-methylimidazole and bi-cyclic nitrogen containing compoundssuch as 1,8-diazabicyclo (5,4,0) undeca-7-ene. The addition amount ofthe curing catalyst is 0.01 to 5% by weight, preferably, 0.05 to 1% byweight based on the total weight of the novolak aralkyl resin and theepoxy resin.

[0062] An organic filler, an inorganic filler, a mixture thereof orother additives may optionally added to the novolak aralkyl resincomposition according to the fourth feature of this invention. It isparticularly preferred to use the organic filler, inorganic filler orthe mixture thereof for improving the mechanical properties or forreducing the entire cost, a colorant such as carbon black for preventingerroneous operation by light and, further, a mold release agent, acoupling agent, a flame retardant such as antimony trioxide and aflexibilizer such as acrylonitrile, butadiene rubber and silicone oil.

[0063] The organic filler, inorganic filler or the mixture thereof to beused can include, for example, powder such as silica, alumina, siliconnitride, silicon carbide, talc, calcium silicate, calcium carbonate,mica, clay and titanium white, and fibers such as glass fibers, carbonfibers and alamide fibers.

[0064] The amount of the organic filler, the inorganic filler or themixture thereof to be used is from 100 to 1900 parts by weight based on100 parts by weight of the novolak aralkyl resin composition. In view ofthe hygroscopic resistance and the mechanical strength, it is preferablyfrom 250 to 1900 parts by weight and, more preferably, from 550 to 1900parts by weight. The novolak aralkyl resin composition according to thefourth feature of this invention can provide a cured product havingexcellent heat resistance and hygroscopic resistance. Accordingly, it isused suitably, for example, to semiconductor encapsulating materials,lamination materials, coatings, adhesives and molding materials.

EXAMPLES

[0065] This invention is to be described more specifically withreference to examples. In the examples, “%” means “% by weight”.Further, the results of various analyses show the values measured by thefollowing methods.

[0066] (1) Ratio of BPF Unit Based on Low Molecular Weight Novolak Unitwith M Being 1 to 4 in the General Formula (1) Described Above inNovolak Aralkyl Resin [wt. %]

[0067] In this invention, the ratio C of BPF unit (m=1) based on the lowmolecular weight novolak unit (m=1−4) in the novolak aralkyl resin isdefined as the ratio of the weight of reacted BPF (ratio reacted as BPFwithout decomposition) based on the weight of the reacted low molecularweight novolak represented by percentage, which is determined by thefollowing equations (1)-(7):

C=100·(W ₁ /W ₂)  (1)

[0068] where W₁: weight of reacted BPF (g), W₂: weight of reacted lowmolecular weight novolak (g).

[0069] W₁ in the equation (1) is represented by the following equation(2):

W ₁ =α·W ₃ −W ₄ −W ₅   (2)

[0070] where α: weight percentage of BPF in low molecular weight novolak(measured value), W₃: weight of low molecular weight novolak used (g)(charged value), W₄: weight of BPF consumed by decomposition (g), W₅:weight of unreacted BPF (g) (measured value).

[0071] W₄ in the equation (2) is represented by the following equation(3):

W ₄=(β·W ₆ /M ₁)·2·M ₂   (3)

[0072] where β: weight percentage of free phenol in the reaction liquidupon completion of aging reaction (measured value), W₆: amount ofreaction liquid (g) upon completion of aging reaction, M₁: molecularweight of phenol (assumed as 94.11), M₂: molecular weight of BPF(assumed as 200).

W ₆ =W ₇ =W ₈   (4)

[0073] since W₇: total charged amount (g) (charged value), W₈: totalamount of distillation liquid from reaction system (g) (measured value),the value for the W₁ can be determined based on the equations (2)-(4).

[0074] On the other hand, W₂ in the equation (1) is represented by thefollowing equation (5):

W ₂ =W ₃ −β·W ₆ −W ₉   (5)

[0075] where W₉: weight of unreacted low molecular weight novolak (g).

[0076] Since most of the unreacted low molecular weight novolak is BPF,

W ₉ =W ₅   (6)

[0077] equation (5) is represented by equation (7) and the value for W₂can be obtained:

W ₂ =W ₃ −β·W ₆ −W ₅   (7)

[0078] (2) Content of Free Phenol in the Novolak Aralkyl Resin and theReaction Liquid (%)

[0079] Analysis is conducted by using a gas chromatograph [model: GC-9A,manufactured by Shimadzu Seisakusho Co.], through columns (insidediameter; 3 mm, length; 2 m) filled with SILICONE OV-1 9.09 wt. % of onCHROMOSOLVE W AW DMCS, using nitrogen as a carrier gas while elevating atemperature from 100° C. to 240° C. at a rate of 10 ° C./min. Thespecimen for analysis is prepared by acetylation with pyridine andacetic acid anhydride. Naphthalene is used as an internal standardsubstance.

[0080] (3) Number of Nuclei of Low Molecular Weight Novolak andMolecular Weight of Novolak Aralkyl Resin

[0081] A high speed liquid chromatograph manufactured by Nippon BunkoCo. (Model: JASCO GULLIVER SERIES) was used and four serially joinedcolumns manufactured by Showa Denko Co. (Model: KF-804, 803, 802, 802]are used. Tetrahydrofuran is used as an eluent. RI (diffraction meter)was used as a detector. The weight average molecular weight (hereinaftersimply referred to as molecular weight or Mw) is indicated as standardpolystyrene converted value.

[0082] (4) Hydroxyl Equivalent of Novolak Aralkyl Resin (g/eq)

[0083] The specimen was accurately weighted by about 1 g in a 200 mlErlenmeyer flask, dissolved with 22.5 ml of pyridine and 2.5 ml ofacetic acid anhydride and, after reacting for 1 hour at 90-100° C., 2 mlof distilled water is added and kept at 100° C. for 30 min. Then, aftercooling, it is titrated with 0.5N sodium hydroxide aqueous solution. Ablank test with no specimen is conducted simultaneously. The equivalentamount is calculated according to the following equation.

OHeq=(1000 w)/{0.5 F(B−A)}

[0084] where OHeq: hydroxyl equivalent (g/eq), w: weight of specimen, B:amount of 0.5N sodium hydroxide aqueous solution (ml) required for blanktest, A: amount of 0.5N sodium hydroxide aqueous solution (ml) requiredfor specimen, F: titer of 0.5N sodium hydroxide aqueous solution.

[0085] (5) Properties of Novolak Aralkyl Resin Composition According tothe Third Feature of the Invention

[0086] (5)-1 Curing Time of Novolak Aralkyl Resin Composition (min)

[0087] Curing property was measured at 150° C. and 160° C. for thenovolak aralkyl resin compositions obtained in Preparation Examples 1-9and Comparative Preparation Example 1-5 by using a curust meter (ModelVDP, manufactured by Orientech Co.), and the time reaching 90% value forthe maximum torque was measured and determined as a curing time.

[0088] (5)-2 Weight Retention Ratio (%) at 300° C. of Novolak AralkylResin Composition

[0089] 4.5 g of a resin composition obtained each by PreparationExamples 5 and 8 and Comparative Preparation Examples 2, 4 and 5 isfilled in a lower metal mold of a curust meter (Model; VDP manufacturedby Orientech Co.) heated previously to 150° C. and kept for 2 minutesand 30 seconds till a portion of the resin composition is melted and itsvolume is to be held in the metal mold. Then an upper metal mold islowered and usual measurement was conducted for 20 minutes and moldingproducts with no bubbles are prepared each by three on each of thespecimens. The molding product is placed in a gear oven and temperatureis elevated to 240° C. for 2 hours. Then, after storing for 1 hour, itis gradually cooled to a room temperature for 1.5 hours or more (theheat treatment is referred to as postcure). After measuring the weightof the post cured molding product, it is stored in a gear oven at 300°C. The weight at the instance the preservation time reaches 24, 96, 144,192 and 240 hours is measured respectively, the weight retention ratio(%) is calculated in accordance with the following equation and shown byan average value.

W _(re)=100·(W ₁₁ /W ₁₀)

[0090] where Wre: weight retention ratio (%), W₁₀: weight of post curedmolding product (g), W₁₁: weight of molded product after preserved at300° C. for a predetermined time (g).

[0091] (5)-3 Molding Time of Novolak Aralkyl Resin CompositionContaining Molding Base Material (min.)

[0092] 300 g of specimens each obtained in Preparation Example 10 andComparative Preparation Example 6 is placed in a metal mold of 95 mmlength, 95 mm width and 70 mm depth, which is pressurized to 9.8 MPabetween two press plates and preliminarily molded at a room temperatureand being out of the metal mold. Successively, the preliminarily moldedmolding material composition is placed in the metal mold of 100 mmlength, 100 mm width and 50 mm depth heated previously to 160° C. byputting between two press plates heated to 160° C., and pressed at 12.75MPa. Then, pressure molding is conducted for a predetermined periodwhile degassing once on every 15 seconds till lapse of 3 minutes andeach once after lapse of 4 minutes and 5 minutes respectively.Instantly, the Rockwell hardness (HRR scale) at the surface of theresultant molding product is measured by the method according to JISK-6911.

[0093] For the evaluation of the molding rate, the pressure molding time(min.) till the hardness reaches the maximum value is measured. ModelTD-37 manufactured by Toho International Co. is used as a moldingmachine, and Model ATK-F200 manufactured by Akashi Seisakusho Co. isused for the Rockwell hardness meter.

[0094] (6) Characteristics of Novolak Aralkyl Resin CompositionAccording to Fourth Feature of this Invention

[0095] (6)-1 Glass Transition Point of Cured Product Obtained fromNovolak Aralkyl Resin Composition [Tg] (° C.)

[0096] A linear expansion coefficient is measured for the specimens(cured product) obtained in Preparation Example 12 and ComparativePreparation Examples 7 to 8 by using a thermal analyzer (model TMA8146manufactured by Rigaku Co.) (TMA method) and Tg is determined.

[0097] (6)-2 Water Absorptivity of Cured Product Obtained from NovolakAralkyl Resin Composition (wt. %)

[0098] The same specimen as described in the preceding paragraph isimmersed in boiling water at 100° C. for 2 hours and the waterabsorptivity(F: wt. %) is shown by the change of weight before and afterimmersion. F is calculated according to the following equation.

F=[(A−B)/B]×100 (wt. %)

[0099] A: weight of cured product after immersion in water,

[0100] B: weight of cured product before immersion in water.

Example 1

[0101] <Preparation of Novolak Aralkyl Resin A>

[0102] To a 500 ml separable flask equipped with a thermometer, astirrer and a condenser, 200 g of a low molecular weight novolak(BPF-ST, trade name of product manufactured by Mitsui Chemicals Inc.,composition: BPF 99.7%, tri-nuclear novolak 0.3%, molecular weight: 200)and 8 g of methanol were charged and the temperature was elevated in anoil bath while stirring to 145° C. of internal temperature and the lowmolecular weight novolak was melted. Then, a methanol solution of 0.176g of diethyl sulfate adjusted to 10% (hereinafter simply referred to asa diethyl sulfate solution) was added. 15 min after, charging of PXDMwas started and 123.11 g thereof was continuously charged for threehours while distilling off by-produced methanol to conduct condensatingreaction. Further, an aging reaction was conducted for 3.5 hours whilekeeping the internal temperature at 145° C. Then, an aqueous solution of0.4744 g of barium hydroxide adjusted to 4% (hereinafter simply referredto as a barium hydroxide solution) was added, temperature was elevatedto 165° C. for 45 min while conducting a neutralizing reaction and thenmethanol was removed under a reduced pressure to obtain 273 g of anovolak aralkyl resin. The resultant novolak aralkyl resin had amolecular weight of 42510, the hydroxyl equivalent of 138 g/eq, thecontent of the free phenol of 0.19% by weight and the value for theratio C of BPF unit relative to the low molecular weight novolak unitwith m being 1 to 4 in the general formula (1) described above of 98% byweight.

Example 2

[0103] <Preparation of Novolak Aralkyl Resin B>

[0104] To the same apparatus as in Example 1, 200 g of a low molecularweight novolak (BPF-M, trade name of product manufactured by MitsuiChemicals Inc., composition: BPF of 91.5%, tri-nuclear novolak of 7.2%,tetra-nuclear novolak of 1.2%, penta-nuclear novolak of 0.1% andmolecular weight of 206) and 8 g of methanol were charged, thetemperature was elevated in an oil bath to melt the content at 108° C.and then the internal temperature was elevated to 145° C. whilestirring. Then, 0.3196 g of a diethyl sulfate solution was added. 15 minafter, charging of PXDM was started and 118.71 g thereof wascontinuously charged for three hours while distilling off by-producedmethanol to conduct a condensating reaction. Further, an aging reactionwas conducted for 3 hours while keeping the internal temperature at 145°C. Then, 0.8978 g of a barium hydroxide solution was added, temperaturewas elevated to 165° C. for 45 min while conducting a neutralizingreaction and then methanol was removed under a reduced pressure, toobtain 272 g of a novolak aralkyl resin. The resultant novolak aralkylresin had a molecular weight of 73280, the hydroxyl equivalent of 137g/eq, the content of the free phenol of 0.29% by weight and the value Cof 87% by weight.

Example 3

[0105] <Preparation of Novolak Aralkyl Resin C>

[0106] 270 g of a novolak aralkyl resin was obtained in the same manneras in Example 2 except for using 0.3152 g of the diethyl sulfatesolution, 116.63 g of PXDM and 0.8659 g of the barium hydroxidesolution. The resultant novolak aralkyl resin had a molecular weight of34410, the hydroxyl equivalent of 136 g/eq, the content of free phenolof 0.30% by weight and the value C of 87% by weight.

Example 4

[0107] <Preparation of Novolak Aralkyl Resin D>

[0108] 269 g of a novolak aralkyl resin was obtained in the same manneras in Example 2 except for using 0.3144 g of the diethyl sulfatesolution, 114.70 g of PXDM and 0.8587 g of the barium hydroxidesolution. The resultant novolak aralkyl resin had a molecular weight of20160, the hydroxyl equivalent of 135 g/eq, the content of free phenolof 0.33% by weight and the value C of 87% by weight.

Example 5

[0109] <Preparation of Novolak Aralkyl Resin E>

[0110] 336 g of a novolak aralkyl resin was obtained in the same manneras in Example 2 except for using 250 g of BPF-M, 7.5 g of methanol,0.3894 g of the diethyl sulfate solution, 140.85 g of PXDM and 1.0801 gof the barium hydroxide solution. The resultant novolak aralkyl resinhad a molecular weight of 14510, the hydroxyl equivalent of 134 g/eq,the content of free phenol of 0.33% by weight and the value C of 87% byweight.

Example 6

[0111] <Preparation of Novolak Aralkyl Resin F>

[0112] 534 g of a novolak aralkyl resin was obtained in the same manneras in Example 2 except for using a 1000 ml separable flask equipped witha thermometer, a stirrer and a condenser, 400 g of BPF-M, 12 g ofmethanol, 0.6090 g of the diethyl sulfate solution, 221.60 g of PXDM and1.6482 g of the barium hydroxide solution. The resultant novolak aralkylresin had a molecular weight of 11160, the hydroxyl equivalent of 134g/eq, the content of free phenol of 0.36% by weight and the value C of87% by weight.

Example 7

[0113] <Preparation of Novolak Aralkyl Resin G>

[0114] 530 g of a novolak aralkyl resin was obtained in the same manneras in Example 2 except for using 400 g of BPF-M, 12.0 g of methanol,0.615 g of the diethyl sulfate solution, 219.70 g of PXDM and 1.7375 gof the barium hydroxide solution. The resultant novolak aralkyl resinhad a molecular weight of 9550, the hydroxyl equivalent of 133 g/eq, thecontent of free phenol of 0.38% by weight and the value C of 87% byweight.

Example 8

[0115] <Preparation of Novolak Aralkyl Resin H>

[0116] 266 g of a novolak aralkyl resin was obtained in the same manneras in Example 2 except for using 200 g of BPF-M, 6.0 g of methanol,0.3035 g of the diethyl sulfate solution, 107.23 g of PXDM and 0.8323 gof the barium hydroxide solution. The resultant novolak aralkyl resinhad a molecular weight of 7460, the hydroxyl equivalent of 133 g/eq, thecontent of free phenol of 0.38% by weight and the value C of 87% byweight.

Example 9

[0117] <Preparation of Novolak Aralkyl Resin I>

[0118] 263 g of a novolak aralkyl resin was obtained in the same manneras in Example 2 except for using 200 g of BPF-M, 6.0 g of methanol,0.3035 g of the diethyl sulfate solution, 103.88 g of PXDM and 0.8341 gof the barium hydroxide solution. The resultant novolak aralkyl resinhad a molecular weight of 5780, the hydroxyl equivalent of 132 g/eq, thecontent of free phenol of 0.29% by weight and the value C of 87% byweight.

Comparative Example 1

[0119] <Preparation of Novolak Aralkyl Resin J>

[0120] 200 g of the same low molecular weight novolak as in Example 2and 4 g of methanol were charged in the same apparatus as in Example 1,temperature was elevated in an oil bath and, after melting the contentsat 110° C., 0.3369 g of a diethyl sulfate solution was added. Then, theinternal temperature was elevated to 165° C. for 49 min and charging ofPXDM was started. 103.88 g of PXDM was continuously charged for threehours to conduct condensating reaction while distilling off by-producedmethanol. Further, an aging reaction was conducted for 1 hour whilekeeping the internal temperature at 165° C. Successively, 0.9337 g of abarium hydroxide solution was added and, after conducting a neutralizingreaction for 30 min while keeping at the same temperature, methanol andthe like were removed under a reduced pressure to obtain 263 g of anovolak aralkyl resin. The resultant novolak aralkyl resin had themolecular weight of 9530, the hydroxyl equivalent of 132 g/eq, thecontent of free phenol of 2.14% by weight and the C value of 79% byweight.

Comparative Example 2

[0121] <Preparation of Novolak Aralkyl Resin K>

[0122] 262 g of a novolak aralkyl resin was obtained in the same manneras in Example 9 except for using 2.46 g of a diethyl sulfate solution,conducting the aging reaction for 1.5 hours and using 6.71 g of a bariumhydroxide solution. The resultant novolak aralkyl resin had themolecular weight of 11370, the hydroxyl equivalent of 132 g/eq, thecontent of free phenol of 2.35% by weight and C value of 77% by weight.

Comparative Example 3

[0123] <Preparation of Novolak Aralkyl Resin L>

[0124] The steps up to the completion of the aging reaction wereconducted in the same manner as in Example 9 except for using 0.3077 gof a diethyl sulfate solution and changing the time from the addition ofthe diethyl sulfate solution to the start of the charging of PXDM to 35min. Then, it was elevated to a temperature of 165° C. and kept for 4hours without neutralization, to obtain 264 g of a novolak aralkylresin. The resultant novolak aralkyl resin had the molecular weight of9470, the hydroxyl equivalent of 132 g/eq, the content of free phenol of2.10% by weight and the C value of 79% by weight.

[0125] Reaction conditions in Examples 1 to 9 and Comparative Examples 1to 3, as well as the obtained results are shown in Table 1 to Table 3.TABLE 1 Example Example Example Example Example 1 2 3 4 5 Low molecularweight novolak (g) 200(ST) 200(M) 200(M) 200(M) 250 ″ (mol) 1.00 0.9710.971 0.971 1.214 Methanol (g) 8 8 8 8 7.5 Diethyl sulfate catalyst (mmol) 0.1143 0.2075 0.2047 0.2042 0.2529 PXDM (g) 123.11 118.71 116.63114.70 140.85 ″ (mol) 0.741 0.714 0.702 0.690 0.848 Catalyst addition -charge start (min) 15 15 15 15 15 Charge time/reaction temp (Hr)/(° C.)3/145 3/145 3/145 3/145 3/145 Aging reaction (Hr)/(° C.) 3.5/145 3/1453/145 3/145 3/145 Ba(OH)₂ (m mol) 0.1108 0.2096 0.2022 0.2005 0.2522Distillation liquid in reaction (g) 48.2 44.6 44.9 43.6 53.5 Free phenolin the reaction liquid (%) 0.29 0.57 0.57 0.54 0.63 Reaction productyield (g) 273 272 270 269 336 Molecular weight Mw 42510 73280 3441020160 14510 Free phenol in the resin (%) 0.19 0.29 0.30 0.33 0.33Hydroxyl equivalent (g/eq) 138 137 136 135 134 Unreacted BPF in theresin (%) 8.8 8.2 8.6 9.0 9.6 Softening point (° C.) — 117 111.5 107.5106.5 C value (wt %) 98 87 87 87 87 Resin name A B C D E Resincomposition name in preparation example AA BB CC DD EE Molding materialresin composition name in preparation example

[0126] TABLE 2 Example 6 Example 7 Example 8 Example 9 Low molecularweight novolak (g) 400(M) 400(M) 200(M) 200(M) Low molecular weightnovolak (mol) 1.942 1.942 0.971 0.971 Methanol (g) 12 12 6 6 Diethylsulfate catalyst (m mol) 0.4013 0.3994 0.1971 0.1971 PXDM (g) 221.60219.70 107.23 103.88 PXDM (mol) 1.333 1.322 0.645 0.625 Catalystaddition - charge start (mm) 15 15 15 15 Charge time/reaction temp(Hr)/(° C.) 3/145 3/145 3/145 3/145 Aging reaction (Hr)/(° C.) 3/1453/145 3/145 3/145 Ba(OH)₂ (m mol) 0.3848 0.4056 0.1943 0.1947Distillation liquid in reaction (g) 85.4 82.8 40.6 39.4 Free phenol inthe reaction liquid (%) 0.61 0.54 0.62 0.65 Reaction product yield (g)534 530 266 263 Molecular weight Mw 11160 9550 7460 5780 Free phenol inthe resin (%) 0.36 0.38 0.38 0.29 Hydroxyl equivalent (g/eq) 134 133 133132 Unreacted BPF in the resin (%) 9.6 9.9 10.4 11.1 Softening point (°C.) 104.5 103.5 100.5 97.5 C value (wt %) 87 87 87 87 Resin name F G H IResin composition name in preparation FF GG HH II example Moldingmaterial resin composition FFF name in preparation example

[0127] TABLE 3 Comp.Exam Comp.Exam Comp.Exam 1 2 3 Low molecular weightnovolak (g) 200(M) 200(M) 200(M) Commercial Commercial ″ (mol) 0.9710.971 0.971 phenol aralkyl novolak Methanol (g) 4 6 6 resin XL-225 typephenol resin #2000 Diethyl sulfate catalyst (m mol) 0.2188 1.597 0.1998PXDM (g) 103.88 103.88 103.88 ″ (mol) 0.625 0.625 0.625 Catalystaddition - charge start (min) 49 15 35 Charge time/reaction temp (Hr)/(°C.) 3/165 3/145 3/145 Aging reaction (Hr)/(° C.) 1/165 1.5/145 3/145Ba(OH)₂ (m mol) 0.2180 1.567 0 Distillation liquid in reaction (g) 40.1541.75 40.0 Free phenol in the reaction liquid (%) 2.25 2.71 2.15Reaction product yield (g) 263 262 264 — — Molecular weight Mw 953011370 9470 11970 2850 Free phenol in the resin (%) 2.14 2.35 2.10 3.73.1 Hydroxyl equivalent (g/eq) 132 132 132 185 106 Unreacted BPF in theresin (%) 7.7 7.0 8.2 — 9.8 Softening point (° C.) 98.5 99.0 98.0 93 96C value (wt %) 79 77 79 0 0 Resin name J K L M N Resin composition namein JJ KK LL MM NN preparation example Molding material resin compositionMMM name in preparation example

Preparation Examples 1 to 9 and Comparative Preparation Examples 1 to 5

[0128] <Preparation of Novolak Aralkyl Resin Composition According toThird Feature of this Invention>

[0129] Novolak aralkyl resin compositions AA-LL, and MM and NN wereproduced by adding 12 parts by weight of hexamine to 100 parts by weightof each of novolak aralkyl resins A-I obtained in Examples 1 to 9, andnovolak aralkyl resins J-L obtained in Comparative Examples 1 to 3, aswell as commercial phenol aralkyl resin (XL-225: trade name of productmanufactured by Mitsui Chemicals Inc., free phenol content of 3.7% byweight, hydroxyl equivalent of 185 g/eq, molecular weight of 11970, Cvalue of 0% by weight) M and commercial novolak type phenol resin(novolak #2000: trade name of product manufactured by Mitsui ChemicalsInc., phenol content of 3.1% by weight, hydroxyl equivalent of 106 g/eq,molecular weight of 2850, C value of 0% by weight) N, and finelypowdered while mixing in a pulverizer.

[0130] (1) Measurement for Curing Time

[0131] The curing time was measured by the method described above forthe novolak aralkyl resin compositions AA-II (Preparation Examples 1 to9), novolak aralkyl resin compositions JJ-LL (Comparative PreparationExamples 1 to 3), resin compositions MM and NN obtained from thecommercial phenol aralkyl resin and the novolak type phenol resin(Comparative Preparation Examples 4 to 5). The result obtained are shownin Table 4. TABLE 4 Measuring result for curing time Preparation ExampleCuring time (min) Comparative preparation example Curing time (min)(resin composition name) 150° C. 160° C. (resin composition name) 150°C. 160° C. Preparation Example 1 (AA) 10.9 Comparative preparationexample 1 (JJ) 10.1 Preparation Example 2 (BB) 10.9 Comparativepreparation example 2 (KK) 10.3 Preparation Example 3 (CC) 10.6Comparative preparation example 3 (LL) 10.1 Preparation Example 4 (DD)10.1 Comparative preparation example 4 (MM) 20.6 16.5 PreparationExample 5 (EE) 10.0 Comparative preparation example 5 (NN) 5.4Preparation Example 6 (FF) 10.1 6.2 Preparation Example 7 (GG) 9.9Preparation Example 8 (HH) 9.8 Preparation Example 9 (II) 9.6

[0132] (2) Measurement for Heat Resistance

[0133] Weight retention ratio at 300° C. was measured by the methoddescribed above for evaluating the heat resistance of the novolakaralkyl resin compositions EE and HH obtained in Preparation Examples 5and 8, as well as resin compositions KK, MM and NN obtained in theComparative Preparation Examples 2, 4 and 5. The results obtained areTable 5. TABLE 5 Measuring result for heat resistance PreparationExample and (resin compo- Weight retention ratio at 300° C. (%)Comparative Preparation Example sition name) 24 hrs 96 hrs 144 hrs 192hrs 240 hrs Preparation Example 5 (EE) 97.8 94.2 91.5 85.8 82.5Preparation Example 8 (HH) 97.6 94.0 90.5 82.7 78.2 ComparativePreparation Example 2 (KK) 97.2 91.1 84.7 72.3 65.9 ComparativePreparation Example 4 (MM) 98.2 95.0 92.7 88.3 85.3 ComparativePreparation Example 5 (NN) 95.5 83.5 68.8 52.0 39.5

Preparation Example 10

[0134] <Preparation of Novolak Aralkyl Resin Composition According tothe Third Feature of this Invention Containing the Molding BaseMaterial>

[0135] 15% by weight of the novolak aralkyl resin composition FF, 5% byweight of Kevler fibers [Dry pulp 979 (2 mm): trade name of productmanufactured by Dupont•Toray•Kevler Co.], 10% by weight of glass fibers[Chopped strand (3 mm): trade name of product manufactured by NipponDenki Glass Co.], 10% by weight of graphite [#2: trade name of productmanufactured by Nippon Graphite Industry Co.], 10% by weight of cashewdust (SENLITE) [FF-1081: trade name of product manufactured by TohokuKako Co.] and 50% by weight of calcium carbonate (NS-200: trade name ofproduct manufactured by Nitto Funka Kogyo Co.] were mixed in a Henschelmixer to obtain a novolak aralkyl resin composition FFF containing amolding base material. The molding time for the resin composition FFFcontaining the molding base material was measured by the methoddescribed above. The results obtained are shown in Table 6.

Comparative Preparation Example 6

[0136] <Preparation of Phenol Aralkyl Resin Composition Corresponding tothe Third Feature of this Invention Containing the Molding BaseMaterial>

[0137] A phenol aralkyl resin composition MMM containing the moldingbase material was obtained in the same manner as in Preparation Example10 for the novolak aralkyl resin composition except for using the phenolaralkyl resin composition MMM instead of the novolak aralkyl resincomposition FF. The molding time of the resin composition MMM containingthe molding base material was measured by the method described above.The results obtained are shown in Table 6. TABLE 6 Measuring result formolding rate Preparation Comparative Preparation Resin composition nameExample 10 Example 6 Molding material resin FF MM composition name FFFMMM Pressure molding Rockwell hardness Rockwell hardness time (min)(HRR) (HRR)  5 −0.2 10 35.9 −22.9 15 51.8 20 63.8 33.5 25 62.2 39.8 3053.4 35 59.2 40 64.0 50 64.0

Preparation Example 11

[0138] <Preparation of Novolak Aralkyl Resin Composition According tothe Third Feature of this Invention Containing Solvent>

[0139] To a 500 ml rounded bottom separable flask equipped with athermometer, a stirrer and a condenser, were charged of the novolakaralkyl resin (D) obtained in Example 4, 60 g of butyl cellosolve and 60g of butyl carbitol, heated to 60 to 70° C., stirred and dissolved.Then, after cooling them to a room temperature, 19.3 g of pulverizedhexamine was added and dissolved while being kept at 30° C. or lower.Successively, the solution was transferred to a pressure filter equippedwith a stainless steel net of 106 μm openings and filtered underpressure with nitrogen to obtain a yellow brown, transparent, viscousnovolak aralkyl resin composition containing the solvent. The specificgravity (25° C./4° C.) was 1.09.

Preparation Example 12 and Comparative Preparation Examples 7 to 8

[0140] <Preparation of Novolak Aralkyl Resin Composition According tothe Fourth Feature of this Invention and Cured Product Thereof>

[0141] As the curing agent, the novolak aralkyl resin H obtained inExample 8 was used in Preparation Example 12, the commercial phenolaralkyl resin (XL-225L: trade name of product manufactured by MitsuiChemicals Inc., free phenol content of 0.5% by weight, hydroxyl groupequivalent of 178 g/eq, molecular weight of 3980 of C value of 0% byweight) was used in Comparative Preparation Example 7, and commercialnovolak type phenol resin (novolak #2000: trade name of productmanufactured by Mitsui Chemicals Inc., phenol content of 3.1% by weight,hydroxyl group content of 106 g/eq, molecular weight of 2850 and C valueof 0% by weight) was used in Comparative Preparation Example 8,respectively. They were pulverized and mixed with the epoxy resin andthe curing catalyst to prepare resin compositions.

[0142] EOCN-102S: trade name of product manufactured by Nippon KayakuCo. was used as the epoxy resin and triphenyl phosphine (TPP) was usedas the curing catalyst. The blending ratio of the epoxy resin, thecuring agent and the curing catalyst was 49 parts by weight of thecuring agent and 1 part by weight of the curing catalyst based on 100parts by weight of the epoxy resin. The obtained resin compositions werecured in a molding die at 175° C. for 5 hours to produce a plate ofabout 2 mm thickness as the curing products. The properties of theobtained cured products were measured by the method described above andthe results are shown in Table 7. TABLE 7 Heat resistance andhygroscopic resistance Comparative Comparative Preparation PreparationPreparation Example 12 Example 7 Example 8 Curing agent Novolak aralkylPhenol aralkyl Novolak-type resin H resin Phenol resin Glass transition163 142 155 point of cured product [Tg] (° C.) Water absorptivity 0.440.44 0.52 of cured product (%)

[0143] <Brief Explanation for the Tables>

[0144] Tables 1 to 3 show the preparation process for the novolakaralkyl resins shown in the examples and the comparative examples, theratio of reacted BPF to the reacted low molecular weight novolak (C),the hydroxyl equivalent, the free phenol concentration and the like. Thehydroxyl equivalent and the like of the commercial phenol aralkyl resinand the novolak type phenol resin are also described in Table 3 forcomparison. Table 4 shows the results of measurement for 90% curing timeof the compositions with hexamine of the novolak aralkyl resin, thephenol aralkyl resin and the novolak type phenol resin shown in thePreparation examples and the comparative preparation examples. Table 5shows the results for the measurement of the heat resistance ofpreparation Examples 5 and 8 and Comparative preparation Examples 2, 4and 5, that is, the compositions with hexamine of the novolak aralkylresin, the phenol aralkyl resin and the novolak type phenol resin. Table6 shows the molding velocity of the molding material resin compositionsof preparation Example 10 and Comparative preparation Example 6, thatis, the compositions of the novolak aralkyl resin and the phenol aralkylresin. Table 7 shows the heat resistance and the hygroscopic resistanceof the resin cured products using each of the novolak aralkyl resin, thephenol aralkyl resin and the novolak type phenol resin as the curingagent for epoxy resin.

[0145] Comparative Example 1 of melting the low molecular weight novolakand elevating the temperature to the reaction temperature after addingthe acidic catalyst is out of the range of this invention in view of thePreparation process and a great amount of free phenol is formed bydecomposition of BPF and the C value of the resultant resin is low,which is out of the scope of this invention. In the same manner, alsoComparative Example 2 out of the scope of this invention in view of thePreparation process with the large addition amount of the acidiccatalyst forms many free phenol due to the decomposition of BPF and theC value of the resultant resin is low, which is out of the range of thisinvention. This resin composition blended with hexamine is deterioratedin the heat resistance. Further, also Comparative Example 3, in whichthe time from the addition of the acidic catalyst to the charging of thearalkyl compound is long and neutralization is not conducted, forms manyfree phenol due to the decomposition of BPF and showing lower C value ofthe resultant resin, which is also out of the scope of this invention.

[0146] On the contrary, in the preparation process according to thisinvention, free phenol due to the decomposition of BPF is formed alittle and the molecular weight can be controlled while keeping the Cvalue of the resultant novolak aralkyl resin higher as it is. Further,in the novolak aralkyl resin composition blended with hexamine accordingto the third feature of this invention, the curing time is greatlyshortened compared with that of the phenol aralkyl resin composition,the heat resistance is much more excellent over the novolak type phenolresins composition and reaches a level approximately to that of thephenol aralkyl resin composition. Further, the rapid curing of thenovolak aralkyl resin composition according to the third feature of thisinvention reflects also on the molding rate of the novolak aralkyl resincomposition containing the molding base material. Further, the novolakaralkyl resin composition according to the fourth feature containing thenovolak aralkyl resin of this invention as a curing agent provides acured product having heat resistance and hygroscopic resistance moreexcellent over the resin composition containing phenol aralkyl resin ornovolak type phenol resin as the curing agent.

What is claimed is:
 1. A preparation process for a novolak aralkyl resinby reacting 0.4 to 0.8 mol of an aralkyl compound based on one mol of alow molecular weight novolak containing 90% by weight or more of abi-nuclear novolak in the presence of an acidic catalyst, whereincomprising at first melting the low molecular weight novolak and heatingit up to a reaction temperature, then adding 0.001 to 0.05% by weight ofthe acidic catalyst based on the total amount of the low molecularweight novolak and the aralkyl compound, then continuously adding thearalkyl compound for reaction, neutralizing the residual acidic catalystafter the completion of the reaction.
 2. A preparation process for anovolak aralkyl resin according to claim 1, wherein the aralkyl compoundis p-xylylene glycol dimethyl ether.
 3. A preparation process for anovolak aralkyl resin according to claim 1, wherein the reactiontemperature is from 130 to 160° C.
 4. A preparation process for anovolak aralkyl resin according to claim 1, wherein the neutralizingagent is hydroxide of at least one metal selected from the groupconsisting of calcium, barium and magnesium.
 5. A novolak aralkyl resinobtained by the preparation process as defined in claims
 1. 6. A novolakaralkyl resin according to claim 5, wherein the novolak aralkyl resin isrepresented by the general formula (1): [Formula 1]

wherein m is an integer of 1 to 4 and n is an integer of 1 to 10,000, inwhich the ratio of the low molecular weight novolak unit with m being 1based on low molecular weight novolak unit with m being 1 to 4 in thegeneral formula (1) described above is at least 80% by weight, thehydroxyl equivalent is 120 to 145 g/eq, and the content of the freephenol is 2% by weight or less.
 7. A novolak aralkyl resin compositioncontaining 80 to 95% by weight of the novolak aralkyl resin as definedin claim 5 and 5 to 20% by weight of hexamethylenetetramine.
 8. Anovolak aralkyl resin composition according to claim 7, wherein the 90%curing time at 150° C. is 7 to 12 minutes and a weight retention ratioafter storage at 300° C. for 240 hours is 70% or more.
 9. A novolakaralkyl resin composition containing 5 to 20% by weight of the resincomposition as defined in claim 7 and 80 to 95% by weight of at leastone molding base material selected from the group consisting ofreinforcing fibers, lubricants and fillers.
 10. A novolak aralkyl resincomposition containing 30 to 70% by weight of the resin composition asdefined in claim 7 and 30 to 70% by weight of at least one solventselected from the group consisting of methanol, ethanol, methyl ethylketone, butyl cellosolve and butyl carbitol.
 11. A novolak aralkyl resincomposition containing 10 to 75% by weight of the novolak aralkyl resinas defined in claim 5, 25 to 90% by weight of an epoxy resin and 0.01 to5% by weight of a curing catalyst based on the total amount of both ofthe resins.
 12. A novolak aralkyl resin composition containing 100 to1900 parts by weight of at least one filler selected from the groupconsisting of organic fillers and inorganic fillers based on 100 partsby weight of the novolak aralkyl resin composition as defined in claim11.
 13. A novolak aralkyl resin cured product obtained by heat curingthe novolak aralkyl resin composition as defined in claim
 11. 14. Anovolak aralkyl resin cured product obtained by heat curing the novolakaralkyl resin composition as defined in claim 12.